I'm so sorry for your loss. I lost a few ducklings when I incubated too. Unfortunately I wasn't able to be there for their passing. I'm always constantly worried about waking up and see my loved ones not moving now. He certainly would have had a difficult life, I have a female crested that can't walk, she finds a lot of happiness and is healthy considering her situation. But shes a lot of work to take care of. Thankfully she learned to eat on her own on her side. But I certainly know the pain that's accompanied with a loss like this. I agree with the above post, the lights going out wasn't the reason why he passed, and that those lights went out for a reason. You'll never have any doubt that he passed in the most comfortable way possible. You're a great mother to those ducklings, and Godbless.
-David